You really can't do anything. Your body is set to the size you are going to be. Your still young so you may fill out more later, but your muscles and such can only get so big based on genetics. Some people are made to be bigger and some are not.
yyyyyyyy would you want thick legs I have em its not always the funnest because some guys LOVE em and some guys HATE em it gets annoying...kinda like girls with big boobs I guess they don't like em but I want em because I don't have em
Don't worry girls don't give a crap about how your legs look. At least some don't.
Try to build your legs muscles
quats, lunges, stiff legged deadlifts, legg press , leg curls, leg flys. sprinting, stair master.
Stop lifting low weight, you need to be lifting at least 80% of your 1 rep maximum on each lift.